以新鲜白萝卜为原料,研究在不同的热风温度、热风风速和切片厚度条件下,白萝卜的热风干燥特性.通过试验数据拟合,比较7种数学模型在白萝卜热风干燥过程中的适用性.结果表明:白萝卜热风干燥以降速过程为主,无明显的恒速阶段.干燥温度、切片厚度对白萝卜的干燥速率影响较大,风速影响较小.干燥温度越高、切片厚度越薄、风速越快,干燥用时越短.通过比较各模型的相关系数(R 2)、卡方值(x2)和均方根误差(RMSE),结果显示Page模型的拟合效果最好,该模型的R2为0.997 6、x2为2.615×10-4、RMSE为0.014 6.且用模型外的试验数据进行验证,也表现出较好的拟合度.白萝卜的有效水分扩散系数(Deff)为7.560×10-10～2.130×10-9,随着干燥温度、风速和切片厚度的增加而增大.白萝卜的干燥活化能为26.34 KJ/mol.此外,还对白萝卜片干燥前后的色差进行了测定和分析,结果表明:在50～80℃时,随着温度的增加,干燥成品的L*值逐渐降低,而b*、a*以及总色差△E*值呈升高的趋势.%With fresh radish as raw materials,the hot-air drying characteristics of fresh radish under different conditions of hot-air temperature,air velocity and slice thickness were investigated in this study.Then the fitting of experimental data and the applicability of 7 different mathematical models for the process of hot-air drying radish was compared.The results showed that the hot-air drying process of radish mainly occured in falling-rate drying period and the constantrate period is not obvious.Hot-air temperature and slice thickness have a greater effect on drying-rate,relatively,while the effects of air velocity is less.The higher the temperature,the thinner the slice and the bigger the air velocity are,the shorter the drying time is.By comparing the coefficients (R2),chi-square values (x2) and the root-mean-square error (RMSE) of each model,it was found that,among these models,the Page model is better than other models for describing the process of hot-air drying radish with R2 of 0.997 6,x2 of 2.615×10-1 and RMSE of 0.014 6.It showed a good fitting between the experimental and predicted values.With the increase of hot-air temperature,air velocity and slice thickness,the effective moisture diffusivity of radish increased from 7.560 × 10-10 to 2.130×10-9,and the activation energy was 26.34 kJ/mol.Finally,the color of dried products under different temperatures was examined and analyzed.Results showed that when the hot-air temperature increased from 50 ℃ to 80 ℃,the L * value showed a gradual decrease,while the values of a *,b * and total chromatism △E* were reductive.
展开▼
